The present invention is in the field of large scale graphic displays such as employed for small computer systems and terminals. The most common technique employed for displays for small computer systems or terminals is a cathode ray tube. In a cathode ray tube, a scanning electron beam having a varying current density is scanned across a light emitting phosphor screen. This light emitting phosphor screen is bombarded by the electron beam and generates light in proportion to the current density of the electron beam. Such displays have the advantage that they are a well known and well understood technology, generate their own light for viewing, can provide a good variation in gray tones and can also provide color. The cathode ray tube is disadvantageous in that it requires a large vacuum enclosing glass envelope which is consequently heavy and bulky. In addition, color producing cathode ray tubes are much more expensive than monochrome tubes and require relatively high driving voltages.
Another display technology used for small computer systems and terminals, especially for those systems which are hand portable or brief case portable, is a liquid crystal display. Each individual pixel within a graphic display has a single liquid crystal display cell which is individually electrically actuatable. These displays have the advantage that they are relatively flat and do not require large drive voltages. Liquid crystal displays are disadvantageous in that they are temperature sensitive, difficult to produce in large sizes, require external light sources for viewing, require a large number of drive lines and extensive drive circuitry and can provide only limited gray scale or color capacity.
Due to the decrease in size and the increase in capacity of small computer systems and terminals, the need for a low cost, high resolution, flexible graphic display device to be employed with these systems is increasing. The prior display technologies such as cathode ray tubes or liquid crystal devices each have disadvantages which preclude them from being ideal for these applications.